Sky could be issued with a hefty fine after Ofcom provisionally ruled that it may have breached broadband switching regulations.
The watchdog has said there are "reasonable grounds" to believe Sky contravened GC9.3 of the General Conditions between May 1st 2015 and July 31st 2015 in respect of landline and broadband services.
The rules are designed to make sure the process of cancelling or switching providers does not deter end users from changing to another firm.
Since this is a provisional ruling from Ofcom, Sky is now being offered the chance to provide written submissions to the watchdog before a final decision is made.
If the outcome goes against Sky, the company could be forced to pay a fine, potentially extending into hundreds of millions of pounds.
Sky has admitted it is "very disappointed" with the regulator's provisional decision and stated that it will review the assessment in detail before putting forward its case.
"We have worked with Ofcom openly and constructively throughout their investigation," a spokesman commented.
The Sky official added that it is "incredibly proud to have the highest customer satisfaction levels in the industry, as ranked in the last Ofcom customer service report".
Research by the regulator found that 80 per cent of Sky Broadband customers were satisfied with the service they received, placing it ahead of the likes of Virgin Media, BT and TalkTalk.
The report also showed that the proportion of customers rating Sky Broadband highly has gone up consistently in the last few years.
In 2012, 63 per cent expressed satisfaction with the provider, and this went up to 71 per cent in 2013 and then to 75 per cent in 2015.
This represented a considerable upturn for Sky Broadband, as satisfaction levels had hovered around the 63-64 per cent mark for several years beforehand.